Generally, for manufacturing of semiconductor device, the gases leaving harmful, flammable, corrosive properties are used. For example, in process for manufacturing the semiconductor device such as Chemical Vapor Deposition (CVD), Low Pressure CVD, Plasma CVD, Plasma Corrosion, and Epitaxy CVD, gas materials such as SiH.sub.4, SiH.sub.2 Cl.sub.2, 4NHl.sub.3, NO, AsH.sub.3, PH.sub.3, B.sub.2 H.sub.6 are a little utilized. Also, a gas exhausted from the device, which carries out the processes, contains a high degree of the toxic components such as harmful, flammable, corrosive properties. Therefore, in order to prevent environmental pollution due to a leakage of the gas materials to atmosphere, it is generally regulated to purify the exhaust gas by the law, before the exhaust gas is exhausted to atmosphere.
There are three methods to dispose the toxic gases produced during manufacturing of the semiconductor device: First method is disposing of flammable toxic components contained in the exhaust gas, which are generally composed of hydrogen gas, by burning the flammable components at high temperature of 500.degree. C. or 800.degree. C. in a burning chamber. Second method is disposing a water-soluble toxic components contained in the exhaust gas by using the wetting method in which the water-soluble toxic components are decomposed while they pass through water stored in the bath. Final method is to remove from the exhaust gas by adsorbing the toxic components contained in the exhaust gas, which cannot be burned or melted, using adsorbents, in which the toxic components are decomposed physically and chemically when they are passing through the adsorbents.
When the burning method is used for disposing the toxic components contained in the exhaust gas, silane contained in the exhaust gas may be burned with oxygen in air, so that Silicon Dioxide is created. Unfortunately such Silicon Dioxide causes following problems: First, the Silicon Dioxide particle could be formed as a result of a gas phase reaction which could clog up gas passages in the burner and in some instances it could cause some troubles in the burning system. Secondly, the Silicon Dioxide is generally collected through a washing process and then water used in the washing process must be treated to completely remove any remaining of chemical particles or other contaminated materials before disposal.
On the other hand, the wetting method has two ways, one being a wet chemical solution which is used to dispose the toxic components contained in the exhaust gas that are water soluble, and the other being a dry chemical solution which is used to dispose them that are non-water soluble material could be dissolved chemically.
However, even tough wetting method is effective in treating the gas produced during the manufacturing of the semiconductor device, it has been less preferred because of the used water or the chemical solution must be cleaned before discharged from a factory corresponding to tendency of gradually strengthen a water pollution regulation world-widely.
Also, the adsorbent method has a problem that the adsorbent must be frequently replaced with new adsorbent because gas passages provided in the agglutinated particles of the adsorbent are clogged with the adsorbed toxic components when the gas is treated by the adsorbent. This causes decrease in the gas flowing rate of the gas that passes through the adsorbent particles.
To overcome the problems set forth above, Delatech Inc, Napa, Calif., U.S., developed CDO.TM. system, as illustrated in FIG. 1, that uses burning method, wetting method, and adsorbent method to dispose the gases that was generated during the manufacturing of the semiconductor device. Followings are the description of how system works.
If the exhaust gas such as gas and/or vapor is entered into the oxidation section 202 of the CDO.TM. system in which an air (O.sub.2) is injected in about pressure of 60 psi into by an air supply nozzle 209, therefore the gas and/or the vapor is mixed with pressured air in the oxidation section 202. Then, mixture of processed exhaust gas and the pressured air flows into the thermal reaction section 203 where thermal/oxidation reaction occurs. In the thermal reactron section 203, the mixtures of the gas and pressured air are heated at the temperature of 650.degree. C. or 900.degree. C. by the cylinder shape of the heater elements 208, in which is provided inconel tubes 210 that was formed by casting an alloy consisting of Fe, Ni, and Cr.
To prevent the mixture of the processed exhaust gas/air from being ignited by heating, N.sub.2 gas is injected at the pressure of 2psi into top of the thermal reaction section 203 when the temperature therein reaches 650.degree. C. by the heater elements 208.
For example, in the thermal reaction section 203, the components such gases as SiH.sub.4, SiH.sub.2 Cl.sub.2, 4NH.sub.3, AsH.sub.3, PH.sub.3, B.sub.2 H.sub.6, and WF.sub.6 contained in the exhaust gas are purified through following heat reactions: ##STR1##
The oxidation nozzle assembly provided in the thermal reaction section 203 is designed to mix the pressured air injected from the air supply nozzle 209 located at the entrance of the thermal reaction section 203 with the exhaust gas. This design controls the location where terminal reaction begins, reduce and/or eliminate particles buildup the air supply nozzle 209, and increase the life of the air supply nozzle 209. The controlled oxygen surrounding is kept at high temperature and enhances heat reaction while it creates effective reactionary mixture. These features enhance the possibility that flammable and toxic gas and vapor will be completely reacted in a contained, controlled manner.
The thermal reaction section 203 as above described is made up of high temperature heater elements 208 isolated from the reactive gas mixture by the inconel tubes 210. The heater elements 208 are a thermocouple that is being controlled to maintain minimum temperature of the thermal reaction section 203.
The reacted gas as above described is then flows into first and second cooling and scrubbing sections 204, 205 by water injected from the water spray nozzles 206, 207, respectively. In the first cooling and scrubbing section 204, the particles, water-soluble components and vapor are removed from the exhaust gas while the gas is cooled at a low temperature, and mixed with water to dissolve water-soluble element. Remaining non-water-soluble toxic components of the exhaust gas are eliminated by the adsorbent 211 provided in the second cooling and scrubbing sections 205 while passing through the second cooling and scrubbing sections 205.
The water, which contains the water-soluble and the adsorbed components, is drained through the drain hole 212 that is located at the bottom of the second cooling and scrubbing section, 205. The drain flow sensor 213 attached at the drain hole 212, senses a water level when it reaches a certain point due to a blockage of the drain hole 212 caused by the water mixture, then closes the water spray nozzle 206, 207 by opening an electric circuit.
However, in CDO.TM. system, because moisture is existed in a boundary between the thermal reaction section 203 and the first cooling and scrubbing section 204, and the particles from the thermal reaction section 203 are mixed with this moisture, then a particle agglomeration is formed therein. This particle agglomeration becomes a blockage of passages in the boundary between the thermal reaction section 203 and the first cooling and scrubbing section 204, which interfere with the gas flow from the thermal reaction section 203 to the first cooling and scrubbing section 204. This will cause a breakdown of the system and as a result shorten the life span of the system.
Moreover, the cost of the system is expensive due to the complexity of the system since it removes the harmful components of the gas by injecting a prescribed pressure of nitrogen, air, and water.
Another inherent problem of above mentioned system is that since the system uses the wetting method, there is a problem of treating water which containing toxic and flammable components, and the chemical adsorbents before releasing from the factory.
Accordingly, an object of present invention is to provided a gas scrubber which can effectively dispose the harmful gas generated during the manufacturing of the semiconductor device as well as is relatively inexpensive gas scrubber since a construction of the system and methods of disposing the gas using the gas scrubber are much simpler.
Another object of the invention is to provide a gas scrubber which can remove clustered harmful particles in much simpler manner and prevent the breakdown of the system due to harmful particles beforehand, thus can be increased the life span of the system, and the methods of disposing the gas using the scrubber.
Further object of the invention is to provide the gas scrubber which can utilize an installation space by placing both burning and adsorption equipment in one case, thus make it compact and light weight, and method of disposing the gas using the scrubber.